1. Field of the Invention
The present invention relates to a variable capacitance element.
2. Description of the Related Art
A known variable capacitance element has an electrostatic capacitance that is varied by changing a permittivity of a dielectric layer by being applied voltage.
For example, International Publication No. 2013/061985 discloses a variable capacitance element including a ferroelectric thin film and a thin film electrode formed by a chemical solution deposition (CSD) method and a sputtering method, respectively.
The element disclosed in International Publication No. 2013/061985 has a relatively large conduction loss because a thickness of an electrode is thin and unable to satisfy a skin depth, and an electrode material is limited to Pt or Au in order to prevent peeling in an annealing treatment after electrode formation so that Ag or Cu with low loss at high frequencies cannot be used. Additionally, since the electrostatic capacitance is acquired from a ferroelectric film FS2 sandwiched by capacitor electrodes PT1 and PT 2 in FIG. 5 of International Publication No. 2013/061985, an electrostatic capacitance value, temperature characteristics, an electrostatic capacitance variable rate, and other properties are determined by the characteristics of the ferroelectric film FS2 and, therefore, the element also has a problem of a small degree of freedom in design of characteristics.